Brick Oscillators For Ham Microwave Operation

Brick Oscillators are one of the most common components used to generate the first Local Oscillator frequency for ham microwave transverters. This is typically around 10.224 GHz for a 10.3681 operating frequency (the recommended calling frequency by the ARRL band plan) and a 2m multi-mode transceiver operating at 144.1 MHz. Unfortunately they require a precision crystal operating typically at 100.22549 MHz (for a 2m IF) which has proven to be hard to find lately.

Brick Oscillators are relatively easily available through eBay (primarily eBay user Pyrojoseph). However, they are not typically directly usable because the crystal is not on a frequency convenient for a direct conversion to 2m or 70 cm IF.

International Crystal Manufacturing used to sell the proper crystals for about $15, but that time is long gone, and the unit price now is more like $65.

I have received a quote from Frequency Management International, and they offer to sell 6 crystals for about $40 each (this is just a price point).

If anyone is interested, please let me know the frequency and quantity, and I will ask for a specific quote. Your guess is as good as mine as to what the price will do when quantities increase, we can probably go around a couple of times refining the quote. I am hoping we can get enough interest to get the price down to $30 or less. That may take 10 crystals or more (my guess).

Personally, I would like to get 2 crystals if the price is around $40, and 3 crystals if the price gets around $30, one for 10.224, one for 10.368.2 for a beacon/marker, and one for 10.512 or 10.800 (I have a brick now set to around 10.750 which will be easier to retune for high side IF).

Please note that the frequency can be adjusted slightly, but it is usually best to adjust it for stronger/more stable oscillation (and to make sure it starts cold) rather than for a specific frequency, so you may end up off by 100kHz or more from your desired frequency. If your IF rig does NOT tune below 144.0, make sure you give yourself plenty of margin.

Also, it is best to avoid using 144.2 to 144.3 as the IF frequency for obvious reasons, unless you live in N-W Florida (I do and there is NIL 2m SSB in my area)

Finally, if you buy more than one crystal to make more than one transverter, I recommend to order them at least 500 kHz apart (as far as the final frequency is concerned) to reduce IF feedthrough if both rigs are used at the same site.

There are links, documents, hints and tools on my web site to help you find crystal frequencies for your particular IF.

http://www.ko4bb.com/cgi-bin/search.pl?search=brick

An alternative would be to develop a low noise PLL or even better a DDS, optionaly locked to GPS, that could be adjusted around 100MHz to drive the brick, instead of using a TO-5 crystal. I have the interest but not the time to do that now. I have been looking at the DDS-60 kit http://www.amqrp.org/kits/dds60/ which, with a different filter, would probably do the job nicely. That kit costs $30, to which we can add a $10 Silabs C8051F530 board to program the DDS, and for about $40, you can have any frequency you like, the cost of a good quality reference oscillator not included…

Didier KO4BB

PS: Here is a link to a web page of interest to microwavers:

http://www.packratvhf.com/Article_6/w3km_picks.htm

Information added March 24, 2009:

To Whom It May Concern:



I have a PLL14-09 Macom brick that works from 1150 to 1160 MHz. I want to
make it work on 1152 MHz. It appears to have output regardless of whether
an input signal is provided or not. Is this normal? How much signal
should
I feed in at 96 MHz? How can I tell when it is locked to the 96 MHz
input?
Any help would be greatly appreciated.



Thanks and 73,



Graham Stratford VE3FHM

Hi Graham,

The PLL14-09 was designed to operate with 10MHz on the input reference. 9.6MHz or 19.2MHz would make it lock on 1152MHz. You can try 96MHz and hope the input limiting amplifier and transformer will allow the lock. The input should be between -10 and +3dBm.

Yes you will still get a random output with no input that will sweep continuously in a 1MHz bandwidth.

Connect an LED in series with a 1Kohm resistor between the +20V brick supply to the alarm pin. When the LED goes off while adjusting the cavity frequency screw the brick will be locked. Once locked measure the DC voltage on the Phase test point and adjust the cavity screw again leaving the voltage on this pin at 8.0V.

Joe KI4NPV